Oxidation inhibited lubricating oil compositions with extreme pressure properties

ABSTRACT

AMIDO-SUBSITUTED DITHIAZOLE-THIONES ARE OXIDATION INHIBITORS FOR LUBRICATING OILS AND IMPART EXTREME PRESSURE PROPERTIES. SAID COMPOUNDS HAVING THE STRUCTURAL FORMULA:   3-(S=),5-(R-CO-N-)-3H-1,2,4-DITHIAZOLE   WHEREIN R IS A HYDROCARBYL GROUP OF AT LAST 8 CARBON ATOMS.

United States Patent O ABSTRACT OF THE DISCLOSURE Amido-substituted dithiazole-thiones are oxidation inhibitors for lubricating oils and impart extreme pressure properties. Said compounds having the structural formula:

wherein R is a hydrocarbyl group of at least 8 carbon atoms.

BACKGROUND OF THE INVENTION Field of the invention This application relates to lubricants possessing superior antioxidant and extreme pressure properties. More particularly, it relates to lubricant compositions containing amido-substituted dithiazole-thiones (i.e., amide-azatrithiones).

Compositions which are employed in the lubrication of modern automobile engines and machinery, or which are used as insulating oils, are subject to attack by oxidation under ordinary operating conditions. When the compositions are attacked by oxidation, a resulting build-up in oxidative products in the lubricants often results in increasing wear upon the parts being lubricated with resultant early failure of the equipment. In turbine oils, the oxidation products (i.e., the acid sludges) corrode the bearings and other parts of the turbine system and clog the oil lines.

The lubricating art has now developed to the point where a large number of oils, both synthetic and natural, are available for many purposes. While these oils vary widely in make-up and in their physical and chemical properties, all, with minor exceptions, have a tendency to become oxidized in the presence of air, especially under the elevated conditions of temperature and pressure encountered in internal combustion engines. This oxidative attack is responsible in part for the formation of the various types of sludges which build up in oils, and which, in the case of oils employed in engines, is responsible for the formation of the solid products which deposit out on the piston and cylinder walls of the engine.

It has also been noted that when oils are oxidized there are formed various acidic and/or peroxidic decomposition products which apparently either cause, or promote, the corrosion of metal surfaces coming into contact with the oil. This corrosive attack becomes particularly severe in the case of metals such as the various copper-lead, cadmium-silver and cadmium-nickel alloys, which are employed in the fabrication of bearings. Further, as these decomposition products are formed, they lead to a progressively more rapid oxidation of the remaining portions of the oil, evidently by a species of chain reation.

It is a tremendous advantage in system design to use oils of sufiicient oxidation stability to permit their use over long periods of time without being changed. It is also desirable that materials employed as additives be nontoxic so 3,753,908 Patented Aug. 21, 1978 as to facilitate safe handling and nonvolatile so that they will remain in the lubricants at elevated temperatures.

Extreme pressure lubrication is characterized by control of friction and wear under high load conditions. It appears to depend on properties of the lubricant other than its viscosity. Friction under extreme pressure conditions generally tends to be higher than that usually associated with fluid film lubrication. The addition of extreme pressure (EP) chemical additives to a lubricating oil can increase the load-carrying capacity of the lubricant many times over. EP additives are thus of considerable economic importance to industry. It was found that the amide-substituted dithiazole-thiones of the present invention function as very effective extreme pressure additives.

Description of the prior art taught as antioxidants in U.S. Pat. No. 2,213,804. Aryltrithiones are taught in U.S. Pat. No. 2,653,910 to be extreme pressure additives. The reaction products of simple trithiones and polyamines were found to be excellent ashless detergents and dispersants according to Anderson U.S. Pat. No. 3,459,664.

SUMMARY The compositions of this invention comprise lubricating oils with an amide-substituted dithiazole-thione to impart antioxidant and extreme pressure properties to the composition. The hydrocarbyl portion of the amide is generally an oil-solubilizing alkyl or alkenyl group of more than 8 carbon atoms. This additive is an ashless antioxidant comparable to the best ashless antioxidants and also imparts extreme pressure properties to the lubricating oil composition.

DESCRIPTION OF THE INVENTION It is our discovery that a high degree of resistance against oxidative attack can be imparted to lubricating oils by incorporating therein an amide-substituted dithiazolethione (i.e., amido-azatrithione). The ashless lubricating oil additive of the present invention is thought to be of the general formula wherein R is a hydrocarbyl of at least 8 carbon atoms. A hydrocarbyl group is one composed solely of H and C atoms. The ring system in the formula is that of a 1,2,4- dithiazole with a thion linkage at the 3 position, sometimes referred to as azatrithione. The 5 position is amidosubstituted.

The hydrocarbyl group, R, is selected from the class comprising alkyl and alkenyl groups of carbon number greater than or equal to 8. R can be the hydrocarbyl portion of a fatty acid, a low molecular weight olefin or a high molecular weight polyolefin. For certain applications, R may also contain aromatic substituents. R can be derived from fatty acids such as oleic acid, linoleic acid, palmitic acid, lauric acid, stearic acid, ricinoleic acid, caprylic acid, etc. R can be an aliphatic or alicyclic branched-chain hydrocarbon radical derived from petroleum hydrocarbons or olefin monomers of from 2-6 carbon atoms having from -2 sites of aliphatic unsaturation, having more than 8 carbon atoms and not more than about 100 carbon atoms, more usually 8-60 carbon atoms and preferably 10-50 carbon atoms.

R can be derived from a polyolefin, as illustrated by polypropylene, polyisobutylene, poly-l-butene, copolymer of ethylene and isobutylene, copolymer of propylene and isobutylene, poly-l-pentene, poly-4-rnethyl-l-pentene, poly-l-hexene, poly-3-methylbutene-1, etc. of average molecular weight from about 300 to about 1,000.

The amido-azatrithione antioxidant and extreme pressure additive is included in the composition in amounts sufi'icient to inhibit oxidation. Amounts of from 0.01 percent to 10 percent by weight are preferred.

v METHOD OF PREPARATION The reaction may ordinarily be carried out inthe temperature range from 0 to 100 C. and preferably at room temperature.

EXAMPLES The following examples typify the preparation of the lubricating oil additives of the present invention.

Example 1 A 125 ml. beaker was charged with g. of C H N S dithiazole-thione, dispersed in 15 cc. of acetonitrile and 2 cc. of pyridine was added. 2.75 g. of palmityl chloride was added dropwise with stirring for about 1 hour at room temperature. The reaction mixture was titrated with H 0 and filtered. The crystals were dissolved in benzene, treated with magnesium sulfate, filtered and recrystallized from benzene. 1.1 g. of product was recovered, melting point 140-142" C. The product was soluble in benzene, insoluble in pentane, and soluble in hot CHCl The product was analyzed as 55 percent C, 8 percent H, 7 percent N, and 26 percent S.

Example 2 A 125 ml. beaker was charged with 5 g. of C H N S 50 cc. of acetonitrile, 7 cc. of pyridine, and 10 g. of oleoyl chloride was added dropwise with stirring for about 1 hour. The reaction mixture was titrated with water, filtered, dissolved in benzene, and the benzene phase was decanted and treated with magnesium sulfate. The product was filtered and recrystallized from hexane. Product yield was about 6.5 g. of waxy material.

Example 3 A 1000 ml. flask was charged with 20 g. of C H N S 250 cc. of acetonitrile, 28 cc. of pyridine, and 40 g. of oleoyl chloride added dropwise with stirring for 2 hours at room temperature. The product was washed repeatedly with water and filtered. The precipitate was dissolved in benzene, filtered and separated from the water phase. The benzene was evaporated via a rotary evaporator at 100 C. and 79.6 g. of crude product were obtained. Recrystallization from methanol yielded 37.1 g. of pure product having a melting point of l19l22 C.

4 Example 4 Into a round-bottomed flask was charged g. of dithiazolethione, 270 cc. of acetonitrile, cc. of pyridine and 34 g. of octanoyl chloride added dropwise. The reac- 5 tion mixture was stirred and refluxed overnight, titrated with water and filtered. The product was 15.2 g. of an oily material soluble in pentane and benzene.

Example 5 Into a 125 ml. flask was charged 1.5 g. of C H N S 10 cc. of acetonitrile, 2 cc. of pyridine and 1.7 g.;of octanoyl chloride added dropwise. The mixture was allowed to stand at room temperature for l hour. 100 cc. of ether'was added, the mixture chilled and the pyridine- 15 HCl filtered off. The cold filtrate was evaporated via the rotary evaporator. f

In order to demonstrate the effectiveness of the compounds of this invention in resisting oxidation, samples of the amide-substituted dithiazole-thione inhibited lubricat- 20 ing oil compositionswere subjected to an oxidation test. The Oxidator B test is our laboratory designation for a test measuring resistance to oxidation by means of a Dornte-type oxygen absorption apparatus (R. W. Dornte, Oxidation of White Oils," Industrial and Engineering 5 Chemistry, vol. 28, p. 26, 1936). Normally, the conditions are one atmosphere of pure oxygen at 340 F. and one reports the hours to absorption of 1000 ml. of 0 by 100 g. of oil. In the Oxidator B test a catalyst is used and a reference additive package is included in the oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oils. Thus, the B method measures the response to conventional inhibitors in a simulated application. The results are given in Table I where the composition of the present invention a is compared to compositions containing other antioxidants.

TAB LE I Oxidator 40 Antioxidant Concentration lifetime 1 Base oil composition 2 1 A 3 18 rnM./ltg. 4. 0 l8 miVL/kg 5. 7 7 1. 6 4. 8

1 Time in hours for 100 grams to take up 1 liter of oxygen. 2 Base oil composition is 5% by weight polyisobutenyl suceinimide and 23% by weight of terephthahe acid in a Vm=480 neutral hydrocarbon.

The test results show that the additives of the present invention are very effective antioxidants. Especially significant is the comparison with the commonly employed zinc dithiophosphate.

The lubricating oils which comprise the basis for the compositions of this invention are those oily or greasy materials employed in lubrication. Examples of these materials are natural and synthetic oils and greases made from these oils, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and mixtures thereof), alkylene oxide-type polymers (e.g., alkylene oxide polymers prepared by polymerization of alkylene oxide, e.g., propylene oxide polymers, etc., in the presence of water or alcohols, e.g., ethyl alcohol), carboxylic acid esters (e.g., those which are prepared by esterifying such carboxylic acids as adipic acid, suberic acid, fumaric acid, etc., with such alcohols as butyl alcohol, hexyl alcohol, pentaerythritol, etc.), polymers of silicon, alkyl biphenyl ethers and other ethers, etc.

The base oils can be used individually or in combinations, wherever miscible or wherever made so by use of mutual solvents.

In addition to the inhibitors described in this invention, the lubricating compositions of this invention may also contain other lubricating oil and grease additives such as oiliness agents, extreme pressure agents, rust inhibitors, other oxidation inhibitors, corrosion inhibitors, viscosity index improving agents, dyes, detergents, dispersants, etc. Usually, for oils to be used in an internal combustion engine, the total amount of these additives will range from about 0.1-20 percent by weight, more usually from about 05-10 weight percent. The individual additives may vary in amounts from about 0.01- weight percent of the total composition. In concentrates, the weight percent of these additives will usually range from about 03-60 weight percent.

The amide-substituted dit-hiazole-thiones (amidoazatrithiones) have been tested for EP properties by means of the Falex machine test. In the Falex test, stationary V blocks are pressed on either side of a rotating steel shaft by a nutcracker arrangement of lever arms. Test specimens are immersed in a tank of test lubricant which is at a known temperature. Loading is automatically increased until seizure occurs. This failure point is indicated by shearing of the pin holding the vertical shaft. The load at failure in pounds is taken as a quantitative measure of the EP property of the oil composition. Mineral oils may failure at 600-900 pounds. Oils with moderate EP additives will fail at 1000-2000 pounds and very effective extreme pressure additives will permit loadings in excess of 300 pounds. The extreme pressure properties of the additives of the present invention are illustrated in the Falex test machine results given in Table II.

1 Load at failure in Falex extreme pressure test. 2 See footnote 7 of Table I.

8 Percent by weight in base oil of Table I.

4 See footnote 8 of Table I.

6 We claim: 1. A lubricating oil composition comprising an oil of lubricating viscosity and from 0.02 percent to 10 percent by weight of a dithiazole-thione of the formula wherein R is a hydrocarbyl group of at least 8 carbon atoms.

2. A lubricating oil composition according to claim 1 wherein R is selected from the group consisting of alkyl groups, alkenyl groups, and polyolefins of average molecular weight less than about 1,000.

3. A lubricating oil composition according to claim 1 wherein R is an alkyl or alkenyl group of from 8-50 carbon atoms.

4. A lubricating oil composition according to claim 1 wherein R is oleyl.

5. A lubricating oil composition according to claim 1 wherein R is polyisobutylene of average molecular weight less than about 1,000.

References Cited UNITED STATES PATENTS 2,971,909 2/1961 Fields 260306.8 R X 3,621,030 11/1971 Seltzer 260306.8 R

PATRICK P. GARVIN, Primary Examiner A. H. METZ, Assistant Examiner US. Cl. X.R. 260306.8 R 

